Reliable link layer multicast in a low power wide area network

ABSTRACT

A management device for a low power wide area network can: generate and send, to each constrained wireless network device via a wired gateway, a link layer multicast listener command specifying a listening interval and causing each constrained wireless network device to change from a low-power optimized mode to a listening mode until reception of a multicast data packet within the listening interval; generate collision avoidance parameters including a minimum waiting interval, a maximum waiting interval relative to the listening interval, and a redundancy constant; and instruct the wired gateways to selectively transmit the multicast data packet based on the collision avoidance parameters, wherein each wired gateway responds by waiting a randomly-selected wait interval between the minimum and maximum waiting intervals, and selectively transmitting the multicast data packet only if a received number of the multicast data packet by the corresponding wired gateway is less than the redundancy constant.

TECHNICAL FIELD

The present disclosure generally relates to reliable link layermulticast in a low power wide area network.

BACKGROUND

This section describes approaches that could be employed, but are notnecessarily approaches that have been previously conceived or employed.Hence, unless explicitly specified otherwise, any approaches describedin this section are not prior art to the claims in this application, andany approaches described in this section are not admitted to be priorart by inclusion in this section.

Low power wide area networks (LPWAN) are wireless technologies that canprovide communications for very constrained network devices: “veryconstrained network devices” refer to very resource-constrained wirelesstransceiver devices (e.g., sensor “motes”) that are (or can be) very-lowcost (e.g., five U.S. Dollars ($5) or less), very-low throughput (e.g.,half duplex 60 kbps peak uplink rate, 30 kbps peak downlink rate ofpackets limited to around 1600 bytes maximum transmission unit (MTU)),and that can have very-low power consumption requirements that permitbattery-only operation for ten to fifteen (10-15) years or more. TheInternet Engineering Task Force (IETF) LPWAN Working Group isinvestigating LPWAN technologies (e.g., LoRaWAN, Narrowband IoT, SIGFOX,etc.) that can provide large-scale deployment of such very constrainednetwork devices, for example by providing large coverage areas (e.g., upto 164 dB maximum coupling loss) for a large number (e.g., fifty-fivethousand) of very constrained network devices.

Large-scale deployment of very constrained network devices, however,requires that the LPWAN technologies impose substantial link constraintsto minimize power consumption requirements, for example by utilizingvery low bit rates (e.g., around 10 bit/sec. to 100 kilobits/sec.),messaging constraints (e.g., rates of about 0.1 message/minute to about1 message/minute or less), etc. Hence, such link constraints of someLPWAN technologies can require single-hop wireless communicationsbetween a gateway and a very constrained network device, without use ofany link layer mesh topology or any network layer routing topologyoverlying the wireless network medium; consequently, such linkconstraints may preclude deployments of a network layer (e.g., InternetProtocol (IP)) or network-based operations such as multicasting, IPv6,6TiSCH, etc.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference is made to the attached drawings, wherein elements having thesame reference numeral designations represent like elements throughoutand wherein:

FIG. 1 illustrates an example low power wide area network having anapparatus for establishing reliable link-layer multicast among veryconstrained network devices based on establishing listening intervalsvia wired gateways executing selective transmission according torandomly-selected wait intervals and detected redundancy of a multicastpacket, according to an example embodiment.

FIG. 2 illustrates the wired gateways of FIG. 1 executing the selectivetransmission during a listening interval according to therandomly-selected wait intervals and the detected redundancy of themulticast packet, according to an example embodiment.

FIG. 3 illustrates an example implementation of any one of themanagement device, wired gateways, or very constrained network devicesof FIG. 1, according to an example embodiment.

FIGS. 4A and 4B illustrate a method of establishing reliable link-layermulticast among very constrained network devices via wired gateways,according to an example embodiment.

FIG. 5 illustrates a timing diagram of the listening intervalsestablished by the management device of FIG. 1 for respective multicastpackets, maximum idle intervals between successively-multicast packets,transmission time instances by wired gateways, and next-listeningintervals based on the transmission time instances, according to anexample embodiment.

FIG. 6 illustrates an example of the selective transmission by the wiredgateways, according to an example embodiment.

DESCRIPTION OF EXAMPLE EMBODIMENTS Overview

In one embodiment, a method comprises: generating and sending, by amanagement device for a low power wide area network comprising wiredgateways and constrained wireless network devices each associated withone or more of the wired gateways via a link layer connection, a linklayer multicast listener command to each constrained wireless networkdevice via the associated wired gateway, the link layer multicastlistener command specifying a listening interval selected by themanagement device, the link layer multicast listener command causingeach constrained wireless network device in response to receipt thereofto change from a low-power optimized mode to a listening mode untilreception of a multicast data packet within the listening interval;generating, by the management device, a set of collision avoidanceparameters for execution by each wired gateway, the collision avoidanceparameters including a minimum waiting interval, a maximum waitinginterval relative to the listening interval, and a redundancy constant;and sending, by the management device, an instruction to the wiredgateways to selectively transmit the multicast data packet based on thecollision avoidance parameters, the instruction causing each wiredgateway to wait a randomly-selected wait interval, relative to theminimum waiting interval and the maximum waiting interval, and after thewait interval selectively transmit the multicast data packet only if areceived number of the multicast data packet by the corresponding wiredgateway is less than the redundancy constant.

In another embodiment, one or more non-transitory tangible media areencoded with logic for execution by a machine and when executed by themachine operable for: generating and sending, by the machine implementedas a management device for a low power wide area network comprisingwired gateways and constrained wireless network devices each associatedwith one or more of the wired gateways via a link layer connection, alink layer multicast listener command to each constrained wirelessnetwork device via the associated wired gateway, the link layermulticast listener command specifying a listening interval selected bythe management device, the link layer multicast listener command causingeach constrained wireless network device in response to receipt thereofto change from a low-power optimized mode to a listening mode untilreception of a multicast data packet within the listening interval;generating, by the management device, a set of collision avoidanceparameters for execution by each wired gateway, the collision avoidanceparameters including a minimum waiting interval, a maximum waitinginterval relative to the listening interval, and a redundancy constant;and sending, by the management device, an instruction to the wiredgateways to selectively transmit the multicast data packet based on thecollision avoidance parameters, the instruction causing each wiredgateway to wait a randomly-selected wait interval, relative to theminimum waiting interval and the maximum waiting interval, and after thewait interval selectively transmit the multicast data packet only if areceived number of the multicast data packet by the corresponding wiredgateway is less than the redundancy constant.

In another embodiment, a method comprises receiving, by a wired gatewayproviding a wireless link layer connection for one or more constrainedwireless network devices in a low power wide area network, a link layermulticast listener command for each of the one or more constrainedwireless network devices, each link layer multicast listener commandreceived via a wired connection with a management device and specifyinga listening interval; transmitting, by the wired gateway, each linklayer multicast listener command to the corresponding constrainedwireless network device, the link layer multicast listener commandcausing the corresponding constrained wireless network device inresponse to receipt thereof to change from a low-power optimized mode toa listening mode until reception of a multicast data packet within thelistening interval; receiving an instruction, from the managementdevice, for selective transmission of the multicast data packet based oncollision avoidance parameters specified in the instruction, thecollision avoidance parameters including a minimum waiting interval, amaximum waiting interval relative to the listening interval, and aredundancy constant; and selectively transmitting, by the wired gateway,the multicast data packet based on randomly selecting a wait intervalrelative to the minimum waiting interval and the maximum waitinginterval, waiting the wait interval following initiation of thelistening interval, and after the wait interval selectively transmittingthe multicast data packet only if the wired gateway has wireles slyreceived less than the redundancy constant of the multicast data packetsfrom one or more other wired gateways.

In another embodiment, one or more non-transitory tangible media areencoded with logic for execution by a machine and when executed by themachine operable for: receiving, by the machine implemented as a wiredgateway providing a wireless link layer connection for one or moreconstrained wireless network devices in a low power wide area network, alink layer multicast listener command for each of the one or moreconstrained wireless network devices, each link layer multicast listenercommand received via a wired connection with a management device andspecifying a listening interval; transmitting, by the wired gateway,each link layer multicast listener command to the correspondingconstrained wireless network device, the link layer multicast listenercommand causing the corresponding constrained wireless network device inresponse to receipt thereof to change from a low-power optimized mode toa listening mode until reception of a multicast data packet within thelistening interval; receiving an instruction, from the managementdevice, for selective transmission of the multicast data packet based oncollision avoidance parameters specified in the instruction, thecollision avoidance parameters including a minimum waiting interval, amaximum waiting interval relative to the listening interval, and aredundancy constant; and selectively transmitting, by the wired gateway,the multicast data packet based on randomly selecting a wait intervalrelative to the minimum waiting interval and the maximum waitinginterval, waiting the wait interval following initiation of thelistening interval, and after the wait interval selectively transmittingthe multicast data packet only if the wired gateway has wireles slyreceived less than the redundancy constant of the multicast data packetsfrom one or more other wired gateways.

DETAILED DESCRIPTION

FIG. 1 illustrates an example low power wide area network 10 having anapparatus (e.g., a network manager device, management device, networkserver device, etc.) 12 configured for establishing reliable link-layermulticast among very constrained network devices (e.g., “N1” to “N4”) 14based on establishing listening intervals (30 of FIG. 5) via wiredgateway devices (e.g., “G1” through “G11”) 16, according to an exampleembodiment: the wired gateways 16 are configured for executing, withinthe established listening intervals 30, selective transmission of amulticast packet (18 of FIG. 2) via wireless data links 20 according torandomly-selected wait intervals and detected redundancy.

Particular embodiments enable very constrained wireless network devices(i.e., constrained wireless network devices) 14 to reliably receive oneor more multicast data packets 18 in a low power wide area network 10based on link layer multicast listener commands 22 generated by amanagement device 12, with minimal power requirements for the veryconstrained wireless network devices 14. The management device 12 cangenerate and send, to each very constrained wireless network device(e.g., “N1”) 14, a corresponding link layer multicast listener command22 via a wired gateway (e.g., “G1”) 16 associated with the veryconstrained wireless network device (e.g., “N1”) 14: the wired gateway(e.g., “G2”) can execute a unicast transmission of the correspondinglink layer multicast listener command 22 to the very constrainedwireless network device (e.g., “N2”) 14 via a link layer connectionimplemented as a wireless data link 20.

As described below, the link layer multicast listener command 22 cancause the very constrained wireless network device 14 to change from alow-power optimized mode (e.g., LoRa Class A or B) to a listening modeuntil reception of a multicast data packet 18 within a listeninginterval 30 specified in the link layer multicast listener command 22. Aconstrained wireless network device (e.g., “N3”) 14 also can transmit alistener command acknowledgement 24 to the management device 12 via thecorresponding associated wired gateway (e.g., “G6”); hence, a wiredgateway (e.g., “G11”) can forward a received listener commandacknowledgement 24 (e.g., from a constrained wireless network device“N4” 14) to the management device 12 via a wired data link 26.

The management device 12 also can generate a set of collision avoidanceparameters for execution by each wired gateway 16, including for examplea minimum waiting interval (Imin), a maximum waiting interval (Imax),and a redundancy constant (k), for example according to the Tricklealgorithm specified in the IETF Request for Comments (RFC) 6206. Asillustrated in FIG. 2, the collision avoidance parameters can cause thewired gateways 16 to selectively transmit a multicast data packet (e.g.,according to the Trickle algorithm), enabling the wired gateways 16 tomulticast the multicast data packet 18 among the very constrainedwireless network devices 14 operating in listening mode during thelistening interval 30.

As described in further detail below, FIG. 2 illustrates that within thelistening interval 30 for a corresponding multicast packet 18, at time“t=t1” a wired gateway “G7” 16 can wirelessly transmit the multicastdata packet 18, at time “t=t2” (t2>t1) the wired gateway “G2” 16 canwireless transmit the same multicast data packet 18 after the wiredgateway “G7” 16, at time “t=t3” (t3>t2) the wired gateway “G1” 16 canwireless transmit the same multicast data packet 18 after the wiredgateway “G2” 16, and at time “t=t4” (t4>t3) the wired gateway “G11” 16can wireless transmit the same multicast data packet 18 after the wiredgateway “G1” 16. The management device 12 and the wired data links 26are omitted from FIG. 2 to avoid cluttering the Figure.

The management device 12 can provide LPWAN link constraints in the lowpower wide area network 10 to minimize power consumption requirements ofthe constrained wireless network devices 14: example LPWAN linkconstraints can include very low bit rates, messaging constraints, anddeployment of the wired gateways 16 to provide single-hop wirelesscommunications with the constrained wireless network devices 14 viawireless data links 20 on a wireless network medium, without the use ofany link layer mesh topology or any network layer routing topologyoverlying the wireless network medium. Hence, the management device 12can establish the reliable link layer multicast as described hereinwithout any link layer mesh topology or any network layer routingtopology or any routing protocol such as the Routing Protocol for LowPower and Lossy Networks (RPL) as described in RFC 6550, etc.

Hence, example embodiments enable reliable transmission of multicastdata packets 18 in a low power wide area network 10 that can beimplemented as a mesh-free and network topology-free network, based onthe management device 12 establishing listening intervals 30 forrespective multicast data packets 18, enabling a very constrainedwireless network device 14 to change from a low-power optimized mode toa listening mode until reception of the multicast data packet 18. Asdescribed below, example embodiments further enable each veryconstrained wireless network device 14 to enter or resume the low-poweroptimized mode in response to receipt of the multicast data packet 18,until initiation of the next listening interval 30 that can be selectedand identified by the management device 12 at or before transmission ofthe multicast data packet 18. The example embodiments also ensure thewired gateways 16 can provide reliable link layer multicast of themulticast data packet 18 based on the redundancy constant, whileavoiding collisions.

Although only the wired gateways “G1”, “G2”, “G6”, “G7”, and “G11” arelabeled with the reference numeral “16” in FIGS. 1-2 to avoid clutteringin the Figures, it should be apparent that all the wired gateways “G1”through “G11” are allocated the reference numeral “16” for purposes ofthe description herein. Further, it should be apparent that all thewired gateways “G1” through “G11” are configured for establishingwireless data links 20, even though only the wired gateways “G1”, “G2”,“G6”, “G7”, and “G11” are shown in FIGS. 1-2 to have wireless data links20 to avoid cluttering in the Figures. Further, each of the constrainedwireless network devices 14 is configured for establishing a wirelessdata link 20, even though only the constrained wireless network device“N3” is shown in FIG. 1 to have a wireless data link 20 to avoidcluttering in the Figures.

FIG. 3 illustrates an example implementation of any one of the devices12, 14, and/or 16, according to an example embodiment. Each apparatus12, 14, and/or 16 is a physical machine (i.e., a hardware device)configured for implementing network communications with other physicalmachines via the low power wide area network 10.

Each apparatus 12, 14, and/or 16 can include a device interface circuit32, a processor circuit 34, and a memory circuit 36. The deviceinterface circuit 32 can include one or more distinct physical layertransceivers for communication with any one of the other devices 12, 14,and/or 16; the device interface circuit 32 also can include an IEEEbased Ethernet transceiver for communications with the devices of FIG. 1via any type of data link (e.g., a wired or wireless link, an opticallink, etc.). The processor circuit 34 can be configured for executingany of the operations described herein, and the memory circuit 36 can beconfigured for storing any data or data packets as described herein. Theterm “configured for” or “configured to” as used herein with respect toa specified operation refers to a device and/or machine that isphysically constructed and arranged to perform the specified operation.

Any of the disclosed circuits of the devices 12, 14, and/or 16(including the device interface circuit 32, the processor circuit 34,the memory circuit 36, and their associated components) can beimplemented in multiple forms. Example implementations of the disclosedcircuits include hardware logic that is implemented in a logic arraysuch as a programmable logic array (PLA), a field programmable gatearray (FPGA), or by mask programming of integrated circuits such as anapplication-specific integrated circuit (ASIC). Any of these circuitsalso can be implemented using a software-based executable resource thatis executed by a corresponding internal processor circuit such as amicroprocessor circuit (not shown) and implemented using one or moreintegrated circuits, where execution of executable code stored in aninternal memory circuit (e.g., within the memory circuit 36) causes theintegrated circuit(s) implementing the processor circuit to storeapplication state variables in processor memory, creating an executableapplication resource (e.g., an application instance) that performs theoperations of the circuit as described herein. Hence, use of the term“circuit” in this specification refers to both a hardware-based circuitimplemented using one or more integrated circuits and that includeslogic for performing the described operations, or a software-basedcircuit that includes a processor circuit (implemented using one or moreintegrated circuits), the processor circuit including a reserved portionof processor memory for storage of application state data andapplication variables that are modified by execution of the executablecode by a processor circuit. The memory circuit 36 can be implemented,for example, using a non-volatile memory such as a programmable readonly memory (PROM) or an EPROM, and/or a volatile memory such as a DRAM,etc.

Further, any reference to “outputting a message” or “outputting apacket” (or the like) can be implemented based on creating themessage/packet in the form of a data structure and storing that datastructure in a non-transitory tangible memory medium in the disclosedapparatus (e.g., in a transmit buffer). Any reference to “outputting amessage” or “outputting a packet” (or the like) also can includeelectrically transmitting (e.g., via wired electric current or wirelesselectric field, as appropriate) the message/packet stored in thenon-transitory tangible memory medium to another network node via acommunications medium (e.g., a wired or wireless link, as appropriate)(optical transmission also can be used, as appropriate). Similarly, anyreference to “receiving a message” or “receiving a packet” (or the like)can be implemented based on the disclosed apparatus detecting theelectrical (or optical) transmission of the message/packet on thecommunications medium, and storing the detected transmission as a datastructure in a non-transitory tangible memory medium in the disclosedapparatus (e.g., in a receive buffer). Also note that the memory circuit36 can be implemented dynamically by the processor circuit 34, forexample based on memory address assignment and partitioning executed bythe processor circuit 34.

FIGS. 4A and 4B illustrate a method of establishing reliable link-layermulticast among very constrained network devices via wired gateways,according to an example embodiment. The operations described withrespect to any of the Figures can be implemented as executable codestored on a computer or machine readable non-transitory tangible storagemedium (i.e., one or more physical storage media such as a floppy disk,hard disk, ROM, EEPROM, nonvolatile RAM, CD-ROM, etc.) that arecompleted based on execution of the code by a processor circuitimplemented using one or more integrated circuits; the operationsdescribed herein also can be implemented as executable logic that isencoded in one or more non-transitory tangible media for execution(e.g., programmable logic arrays or devices, field programmable gatearrays, programmable array logic, application specific integratedcircuits, etc.). Hence, one or more non-transitory tangible media can beencoded with logic for execution by a machine, and when executed by themachine operable for the operations described herein.

In addition, the operations described with respect to any of the Figurescan be performed in any suitable order, or at least some of theoperations can be performed in parallel. Execution of the operations asdescribed herein is by way of illustration only; as such, the operationsdo not necessarily need to be executed by the machine-based hardwarecomponents as described herein; to the contrary, other machine-basedhardware components can be used to execute the disclosed operations inany appropriate order, or execute at least some of the operations inparallel.

Referring to FIG. 4A, the processor circuit 34 of the management device12 in operation 40 is configured for identifying one or more multicastdata packets (e.g., M1, M2, . . . Mn) 18 for multicasting in the lowpower wide area network 10, described previously as a mesh-free networkand network topology-free network (e.g., according to LoRA, LPWAN,etc.). For example, the wired device interface circuit 32 of themanagement device 12 in operation 40 can receive a data structure froman external source (e.g., a server device via a local and/or wide areanetwork such as the Internet), and the processor circuit 34 of themanagement device 12 can determine that the data structure (e.g.,comprising executable code and/or data parameters) needs to befragmented into data fragments for multicast transmission to theconstrained wireless network devices 14 as multicast data packets (e.g.,M1, M2, M3) 18. Hence, the processor circuit 34 of the management device12 in operation 40 can fragment the data structure into identifiedmulticast data packets (e.g., M1, M2, M3). The data fragments can beidentified by respective index values, for example using LPWAN StaticContext Header Compression (SCHC).

As illustrated in FIG. 5, The processor circuit 34 of the managementdevice 12 in operation 42 can compute a schedule 44 for multicasting themulticast data packets 18, where the schedule 44 comprises a listeninginterval “T1” 30 for each multicast data packet 18. For example, theprocessor circuit 34 of the management device 12 in operation 42 canestablish the listening interval “T1_M1” 30 a for the multicast datapacket “M1” 18, the listening interval “T1_M2” 30 b for the multicastdata packet “M2” 18, and the listening interval “T1_M3” 30 c for themulticast data packet “M3” 18. The processor circuit 34 of themanagement device 12 can determine that the listening intervals 30 a, 30b, and/or 30 c have the same time duration, or different time durations,as appropriate.

The processor circuit 34 of the management device 12 in operation 42also can determine that the schedule 44 comprises zero or more timeseparations (i.e., maximum idle intervals) (e.g., “T2” 46) betweeninitiation of a first listening interval (e.g., 30 a) at event “t0”(i.e., t=0) 48 for a multicast data packet (e.g., “M1”) 18 andinitiation of a second listening interval (e.g., 30 b) at event “t5” 50for a second multicast data packet (e.g., “M2”) 18. A time separationvalue of “T2=0” 46 can be set to represent simultaneous initiation ofthe first listening interval (e.g., 30 a) for the first multicast datapacket (e.g., “M1”) and the second listening interval (e.g., 30 b) forthe second multicast data packet (e.g., “M2”).

As illustrated in FIG. 5, the processor circuit 34 of the managementdevice 12 in operation 42 can set a time separation “T2_M2” 46acorresponding to initiation of the listening interval “T1_M2” 30 b atevent “t5” 50 following the initiation of the listening interval “T1_M1”30 a at event 48; the processor circuit 34 of the management device 12in operation 42 also can set a time separation “T2_M3” 46 bcorresponding to initiation of the listening interval “T1_M3” at event“t6” 52 following the initiation of the listening interval “T1_M2” 30 bat event “t5” 50. The processor circuit 34 of the management device 12can set each time separation 46 to a value of zero or more milliseconds,seconds, etc.

The processor circuit 34 of the management device 12 in operation 54 ofFIG. 4A can identify targeted constrained wireless network devices 14(e.g., identified “motes” 14) for a multicast group in the mesh-free lowpower wide area network 10. The processor circuit 34 of the managementdevice 12 can generate, for each constrained wireless network device 14in the multicast group, a corresponding link layer multicast listenercommand 22 specifying the corresponding listening interval “T1” 30 forthe associated multicast data packet 18, and the processor circuit 34 ofthe management device 12 in operation 54 can unicast transmit the linklayer multicast listener command 22 to the corresponding targetedconstrained wireless network device (e.g., “N1” of FIG. 1) 14 via theassociated wired gateway (e.g., “G1”) 16.

In one embodiment, the link layer multicast listener command 22 can beimplemented as a LoRa “Class D” command that causes a constrainedwireless network device 14 to respond to receipt of the link layermulticast listener command 22 by changing from a low-power optimizedmode (e.g., LoRa Class A or LoRa Class B) to a listening mode untilreception of the associated multicast data packet 18 within thelistening interval 30. As illustrated in FIG. 1, the device interfacecircuit 32 of the management device 12 can transmit the link layermulticast listener commands 22 via the wired data links 26, enabling themanagement device 12 to unicast transmit in operation 54 a link layermulticast listener command 22 to each constrained wireless networkdevice 14 via an associated wired gateway 16 (e.g., “N1”14 via “G1” 16,“N2” 12 via “G2” 16, “N3” 12 via “G6” 16, and “N4” 14 via “G11” 16).Each link layer multicast listener command 22 generated by themanagement device 12 can specify the listening interval 30 (e.g.,“T1_M1” 30 a) for the next multicast data packet (e.g., “M1”) 18; eachlink layer multicast listener command 22 generated by the managementdevice 12 also can optionally include the maximum idle interval (e.g.,“T2_M2” 46 a) that identifies the initiation of the next listeninginterval (e.g., “T1_M2” 30 b).

The processor circuit 34 of the management device 12 can causetransmission of the link layer multicast listener command 22 to acorresponding constrained wireless network device 14, for example, inresponse to receiving a data packet from the constrained wirelessnetwork device 14 operating in low-power mode (e.g., LoRa Class A). Aconstrained wireless network device 14 operating under LoRa Class A orClass B operation includes two or more listen windows followingtransmission by the constrained wireless network device 14, hence themanagement device 12 can unicast the link layer multicast listenercommand 22 within one of the two LoRa Class A/B listen windows to enablethe constrained wireless network device 14 to receive the link layermulticast listener command 22 within one of its LoRa Class A/B listenwindows.

Each constrained wireless network device 14 can respond in operation 56to reception of link layer multicast listener command 22 by changingfrom the low-power optimized mode to the listening mode until receptionof the multicast data packet 18.

Each constrained wireless network device 14 also can respond to theunicast link layer multicast listener command 22 by transmitting inoperation 56 a listener command acknowledgement 24 to the managementdevice 12 via the associated wired gateway 16 within a prescribed timeinterval. The processor circuit 34 of the management device 12 inoperation 58 optionally can remove from the multicast group anyconstrained wireless network device 14 that does not send acorresponding listener command acknowledgement 24 within a prescribedtime interval following unicast transmission of the link layer multicastlistener command 22.

The processor circuit 34 of the management device 12 in operation 60 cangenerate collision avoidance parameters for selective transmission of amulticast data packet 18 by the wired gateways 16 within a correspondinglistening interval 30. In one embodiment, the collision avoidanceparameters can include Trickle parameters in accordance with RFC 6206,including a minimum waiting interval “Imin”, a maximum waiting interval“Imax” that is based on the listening interval 30, and a redundancyconstant “k”. As described below, each of the wired gateways 16 canselectively transmit a multicast data packet 18 based on the collisionavoidance parameters “Imin”, “Imax”, and “k”, where a given wiredgateway “Gi” 16 can selectively transmit a multicast data packet 18 onlyif, after waiting a randomly-selected wait interval “WI_GWi” followinginitiation of the corresponding listening interval “T1” 30, the givenwired gateway “Gi” 16 has received no more than a number “c” of themulticast data packets 18 that is less than the redundancy constant “k”(i.e., c<k).

The processor circuit 34 of the management device 12 can set the maximumwaiting interval “Imax” relative to the listening interval 30 for themulticast packet, and relative to the redundancy constant “k”, enablingeach constrained wireless network device 14 to “stay awake” to listenfor one or multiple Trickle iterations. As described below, therelationship between a listening interval (e.g., “T1_M_1”) 30 and themaximum waiting interval “Imax” can be set such that the listeninginterval 30 is equal to one or more maximum waiting interval iterations,e.g., the listening interval 30 can equal any one of “Imax”, “3*Imax”,“7*Imax”, etc., enabling a constrained wireless network device 14 tolisten for multiple Trickle iterations “Imax”, then “2*Imax”, then“3*Imax”, etc., as appropriate (the symbol “*” represents amultiplication operation).

In one embodiment, the processor circuit 34 of the management device 12sets the same collision avoidance parameters for all wired gateways 16for all multicast data packets 18; in another embodiment, the managementdevice 12 can use the same collision avoidance parameters for all wiredgateways 16 for a given multicast data packet 18, but change thecollision parameters for different multicast data packets 18 within therespective listening intervals 30 (e.g., selective transmission ofmulticast packets “M1”, “M2”, and “M3” within the respective listeningintervals 30 a, 30 b, and 30 c can be based on different collisionavoidance intervals); in another embodiment, the management device 12can use different sets of collision avoidance parameters for differentwired gateways 16, for example wired gateways 16 identified as belongingto a “dominating set” (DS) can have higher-priority collision avoidanceparameters that result in lower wait intervals “WI_GWi_DS” relative toany wait intervals “WI_GWi” of non-dominating set members. Othervariations of collision avoidance parameters can be established by theprocessor circuit 34 of the management device 12 for any one or moremulticast data packet 18 and/or any one or more wired gateway 16.

The processor circuit 34 of the management device 12 in operation 62 cansend the next multicast data packet (e.g., “Ml”) 18 via the wired datalink 26 to all the wired gateways 16 prior to the initiation of thecorresponding listening interval (e.g., “T1_M_1” 30 a) (e.g., at event“t0” 48). The device interface circuit 32 of the management device 12 inoperation 62 also can send, prior to initiation of the correspondinglistening interval (e.g., at event “t0” 48), an instruction to the wiredgateways 16 to execute the selective transmission of the next multicastdata packet (e.g., “M1”) based on the collision avoidance parameters.

As illustrated in the example sequence diagram in FIG. 6, the managementdevice 12 in operation 62 can send (by event “t0” 48) the multicast datapacket “Ml” 18 and the instructions containing the collision avoidanceparameters “Imin”, “Imax”, and “k” to each wired gateway 16; themanagement device 12 also can output to each wired gateway 16 (by event“t0” 48) the maximum idle interval “T2_M2” 46 a that identifies theinitiation of the listening interval “T1_M2” at event “t5” 50.

The processor circuit 34 of each wired gateway 16 is configured forresponding to the instruction (containing the collision avoidanceparameters) by executing in operation 64 the collision avoidance methodfor selective transmission of the multicast data packet (e.g., “M1”) 18.For example, each wired gateway “Gi” 16 (where “i=1 to 11” for any ofthe wired gateways “G1” through “G11”) can be configured for operatingaccording to the Trickle algorithm under RFC 6206; hence, the processorcircuit 34 of each wired gateway “Gi” 16 can randomly set an interval“I_GWi” to a value in the range between [Imin, Imax] (i.e.,“Imin≤I_GWi≤Imax”); at the beginning of a collision avoidance intervalthe processor circuit 34 of each wired gateway “Gi” 16 also can select arandomly-selected wait interval “WI_GWi” relative to the minimum waitinginterval “Imin” and the maximum waiting interval “Imax” (i.e., betweenone half the interval “I_GWi” and the interval “I_GWi”), for examplewhere “WI_GWi=RND [I_GWi/2, I_GWi]” (i.e., “I_GWi/2≤WI_GWi≤I_GWi”) (and“Imin≤I_GWi≤Imax”).

Hence, each wired gateway “Gi” 16 in operation 64 randomly selects aninterval “I_GWi” between [Imin, Imax], and each wired gateway “Gi” 16 inoperation 64 randomly selects its wait interval “WI_GWi” between“I_GWi/2” and “I_GWi” (the symbol “I” represents a division operation).

Consequently, at the beginning of the listening interval “T1_M1” 30 a atevent “t0” 48 each constrained wireless network device 14 can wake up atoperation 66 of FIG. 6, and each wired gateway 16 can begin waiting itscorresponding wait interval “WI_GWi”.

As illustrated in FIGS. 2, 5, and 6, at event “t1” 68 the wired gateway“G7” 16 can complete its wait interval “WI_GW7” and determine inoperation 64 of FIG. 4A that its receive counter “c” equals zero,indicating no other copies of the multicast data packet “M1” have beenreceived by the wired gateway “G7” 16 from any other wired gateway 16;hence, its counter “c” is less than the redundancy constant “k=2”, i.e.,“c<k”. Hence, the wired gateway “G7” 16 in operation 90 of FIG. 4A andoperation 70 of FIG. 4B and FIG. 6 can determine its transmission timeinstance “T_GW7” for the multicast data packet “M1” 18, and determine anext-listening interval “Tnext7” 72 as the difference between themaximum idle interval “T2_M2” 46a minus the transmission time instance“T_GWi” (e.g., “Tnext7=T2_M2−T_GW7”).

The processor circuit 34 of the device interface circuit 32 of the wiredgateway “G7” 16 in operation 70 of FIGS. 4B and 6 can cause its wirelessdevice interface circuit 32 to transmit the multicast data packet “M1”and the next-listening interval “Tnext7” 72 at event “t1” 68 via thewireless data link 20. Hence, any constrained wireless network device(e.g., “N3”) 14 that can detect the transmission by the wired gateway“G7” 16 at the event “t1” 68 can respond to receiving the multicast datapacket “M1” and the next-listening interval “Tnext7” 72 in operation 74by entering a low-power optimized mode (e.g., “sleep mode” under LoraClass A), and resuming the listening mode upon initiation of the secondlistening interval at event “t5” 50 as identified by the next-listeninginterval “Tnext7” 72.

As illustrated in FIG. 6, each of the wired gateways 16 that detect thewireless transmission of the multicast data packet “M1” by the wiredgateway “G7” 16 at the event “t1” 68 (e.g., wired gateways “G2” through“G6” and “G8” through “G11”) respond in operation 76 by incrementingtheir respective receive counters “c”.

Assume the wired gateway “G2” is the next gateway that completes itswait interval. As illustrated in FIGS. 2, 5, and 6, at event “t2” 78 thewired gateway “G2” 16 can complete its wait interval “WI_GW2” anddetermine in operation 64 of FIG. 4A (80 of FIG. 6) that its receivecounter “c” equals one (“c=1”) and is less than the redundancy constant“k=2” (i.e., “c<k”). Hence, the wired gateway “G2” 16 in operation 70 ofFIG. 4B (80 of FIG. 6) can determine its transmission time instance“T_GW2” for the multicast data packet “M1” 18, and determine anext-listening interval “Tnext2” (not shown in FIG. 5) as the differencebetween the maximum idle interval “T2_M2” 46 a minus the transmissiontime instance “T_GWi” (e.g., “Tnext2=T2_M2−T_GW2”).

The processor circuit 34 of the device interface circuit 32 of the wiredgateway “G2” 16 in operation 70 of FIG. 4B (operation 80 of FIG. 6) cancause its wireless device interface circuit 32 to transmit the multicastdata packet “M1” and the next-listening interval “Tnext2” at event “t2”78 via the wireless data link 20. Hence, any constrained wirelessnetwork device (e.g., “N1” and/or “NT”) 14 that can detect thetransmission by the wired gateway “G2” 16 at the event “t2” 78 canrespond to receiving the multicast data packet “M1” and thenext-listening interval “Tnext2” in operation 74 by entering a low-poweroptimized mode (e.g., “sleep mode” under Lora Class A), and resuming thelistening mode upon initiation of the second listening interval at event“t5” 50 as identified by the next-listening interval “Tnext2”.

As illustrated in FIG. 6, each of the wired gateways 16 that detect thewireless transmission of the multicast data packet “Ml” by the wiredgateway “G2” 16 at the event “t2” 78 (e.g., wired gateways “G1” and “G3”through “G7”) respond in operation 82 by incrementing their respectivereceive counters “c”.

Assume the wired gateway “G1” is the next gateway that completes itswait interval. As illustrated in FIGS. 2, 5, and 6, at event “t3” 84 thewired gateway “G1” 16 can complete its wait interval “WI_GW1” anddetermine in operation 64 of FIG. 4A (86 of FIG. 6) that its receivecounter “c” equals one (“c=1”) and is less than the redundancy constant“k=2” (i.e., “c<k”). Hence, the wired gateway “G1” 16 in operation 70 ofFIG. 4B (86 of FIG. 6) can determine its transmission time instance“T_GW1” for the multicast data packet “M1” 18, and determine anext-listening interval “Tnext1” (not shown in FIG. 5) as the differencebetween the maximum idle interval “T2_M2” 46a minus the transmissiontime instance “T_GWi” (e.g., “Tnext1=T2_M2−T_GW1”).

The processor circuit 34 of the device interface circuit 32 of the wiredgateway “G1” 16 in operation 70 of FIG. 4B (operation 86 of FIG. 6) cancause its wireless device interface circuit 32 to transmit the multicastdata packet “M1” and the next-listening interval “Tnext1” at event “t3”84 via the wireless data link 20. Hence, any constrained wirelessnetwork device 14 that can detect the transmission by the wired gateway“G1” 16 at the event “t3” 84 can respond to receiving the multicast datapacket “M1” and the next-listening interval “Tnext1” in operation 74 byentering a low-power optimized mode (e.g., “sleep mode” under Lora ClassA), and resuming the listening mode upon initiation of the secondlistening interval at event “t5” 50 as identified by the next-listeninginterval “Tnext1”.

As illustrated in FIG. 6, each of the wired gateways 16 that detect thewireless transmission of the multicast data packet “M1” by the wiredgateway “G1” 16 at the event “t3” 84 (e.g., wired gateways “G2” through“G7” and “G9”) respond in operation 88 by incrementing their respectivereceive counters “c”. As noted in FIG. 6, the wired gateways “G3”through “G6” and “G9” 16 defer from any transmission during theircurrent idle interval “I_GWi” in response to determining their receivecounters exceed the redundancy constant “k=2” (i.e., c≥2). Hence, thewired gateways “G3” through “G6” and “G9” 16 in operation 90 of FIG. 4Adetermine they cannot transmit in response to their receive countersequaling or exceeding the redundancy constant, and in response wait inoperation 92 until they can repeat the next collision avoidanceinterval, for example as described in RFC 6206.

Assume the wired gateway “G11” is the next gateway that completes itswait interval. As illustrated in FIGS. 2, 5, and 6, at event “t4” 94 thewired gateway “G11” 16 can complete its wait interval “WI_GW11” anddetermine in operation 64 of FIG. 4A (96 of FIG. 6) that its receivecounter “c” equals one (“c=1”) and is less than the redundancy constant“k=2” (i.e., “c<k”). Hence, the wired gateway “G11” 16 in operation 70of FIG. 4B (96 of FIG. 6) can determine its transmission time instance“T_GW11” for the multicast data packet “M1” 18, and determine anext-listening interval “Tnext11” (not shown in FIG. 5) as thedifference between the maximum idle interval “T2_M2” 46 a minus thetransmission time instance “T_GWi” (e.g., “Tnext1=T2_M2−T_GW11”).

The processor circuit 34 of the device interface circuit 32 of the wiredgateway “G11” 16 in operation 70 of FIG. 4B (operation 96 of FIG. 6) cancause its wireless device interface circuit 32 to transmit the multicastdata packet “M1” and the next-listening interval “Tnext11” at event “t4”94 via the wireless data link 20. Hence, any constrained wirelessnetwork device (e.g., “N4”) 14 that can detect the transmission by thewired gateway “G11” 16 at the event “t4” 94 can respond to receiving themulticast data packet “M1” and the next-listening interval “Tnext11” inoperation 74 by entering a low-power optimized mode (e.g., “sleep mode”under Lora Class A), and resuming the listening mode upon initiation ofthe second listening interval at event “t5” 50 as identified by thenext-listening interval “Tnext11”.

As illustrated in FIG. 6, each of the wired gateways 16 that detect thewireless transmission of the multicast data packet “M1” by the wiredgateway “G11” 16 at the event “t4” 94 (e.g., wired gateways “G4” through“G10”) can respond in operation 98 by incrementing their respectivereceive counters “c”. As noted in FIG. 6, the wired gateways “G3”through “G6” and “G8” through “G10” 16 defer from any transmissionduring their current idle interval “I_GWi” in response to determiningtheir receive counters exceed the redundancy constant “k=2” (i.e., c≥2).Hence, the wired gateways “G3” through “G6” and “G8” through “G10” 16 inoperation 90 of FIG. 4A determine they cannot transmit in response totheir receive counters equaling or exceeding the redundancy constant,and wait in operation 92 until they can repeat the next collisionavoidance interval. Hence, all the wired gateways “G1” through “G11”wait until the repeating next idle interval in operation 92, or untilexpiration of the listening interval 30 a at operation 100.

The above-described method can be repeated for each listening interval(e.g., “T1_M2” 30 b, “T1_M3” 30 c) of the corresponding multicast datapacket (e.g., “M2”, “M3”) 18, until the last multicast data packet(e.g., “M3”) has been multicast in its corresponding listening interval30 c in operation 102, except that in one embodiment, for the last datapacket “M3”, no time separation 46 would be transmitted by themanagement device 12, nor would any wired gateway 16 transmit anext-listening interval 72 with the last multicast data packet “M3”, tonotify each constrained wireless network device 14 that the nextmulticast data packet “M3” is the last multicast data packet in thesequence of multicast data packets associated with the data structurethat was fragmented by the network manager 12 in operation 40. Hence,each wired gateway 16 can identify the last multicast data packet (e.g.,“M3”) in response to a determined absence of a time separation “T2”accompanying the instructions sent by the management device 12 inoperation 62 with the next data packet “M3”; alternately, eachconstrained wireless network device 14 can detect the last multicastdata packet “M3” 18 in response to a determined absence of the timeseparation “T2” 46 (by the management device 12) and/or a determinedabsence of the next-listening interval 72 (by a wired gateway 16transmitting the multicast data packet “M3”).

Alternately, the instructions can include a “last” flag indicating thelast multicast data packet in the sequence of multicast data packets,where the parameter “T2” can be used to specify the final duration ofmulticasting any of the multicast data packets in the sequence ofmulticast data packets (i.e. when all listening intervals for respectivemulticast data packets are to be terminated).

Following multicasting of the last multicast data packet (e.g., “M3”)18, each constrained wireless network device 14 in operation 104 canunicast transmit a bitmap of the received multicast data packets to itsassociated wired gateway 16, where each bit corresponds to a receivedbit; each constrained wireless network device 14 also can unicasttransmit its bitmap in response to detecting that all listeningintervals for the respective multicast packets have been terminated. Inresponse to a wired gateway 16 receiving a bitmap from an identifiedconstrained wireless network device 14, the wired gateway 16 inoperation 106 can identify from the received bitmap any missingmulticast data fragments, and in response the wired gateway 16 canunicast transmit in operation 108 the missing multicast data packet(s)to the constrained wireless network device 14 to ensure reliabledelivery of all the multicast data packets 18. In an alternateembodiment, each bitmap generated by the corresponding constrainedwireless network device 16 can be forwarded by a wired gateway 16 to themanagement device 12, and the management device 12 can cause a selectedone of the wired gateways 16 to unicast transmit the one or more missingdata fragments to the corresponding constrained wireless network device16. The unicast transmission of the bitmap and missing multicast datapackets can be implemented, for example, using LPWAN Static ContextHeader Compression (SCHC).

In another embodiment, a wired gateway 16 can detect from a prescribednumber of received bitmaps from respective constrained wireless networkdevices 14 that a repeat multicast of a missing fragment would bepreferable to repeated unicast transmissions of the missing fragment,and in response send a request to the management device 12 for a repeatmulticast of the missing fragment. The management device 12, in responseto receiving the repeat multicast request from an identified wiredgateway 16, can send an instruction to the identified wired gateway 16for executing a repeat multicast transmission of the missing fragment.

According to example embodiments, reliable link layer multicast can beimplemented in a low power wide area network that utilizes onlysingle-hop link layer connections between constrained wireless networkdevices and wired gateways. The example embodiments enable reliable linklayer multicast without the necessity of any network layer topology orany routing protocol requirements for the constrained wireless networkdevices; hence, the constrained wireless network devices can operateusing minimal data link requirements, for long term battery powerconservation. Further, the collision-avoidance methods deployed in thewired gateways under the control of the management device enable aminimized and controlled multicasting on the wireless data links,regardless of the density of the wired gateways in the low power widearea network.

While the example embodiments in the present disclosure have beendescribed in connection with what is presently considered to be the bestmode for carrying out the subject matter specified in the appendedclaims, it is to be understood that the example embodiments are onlyillustrative, and are not to restrict the subject matter specified inthe appended claims.

What is claimed is:
 1. A method comprising: generating and sending, by amanagement device for a low power wide area network comprising wiredgateways and constrained wireless network devices each associated withone or more of the wired gateways via a link layer connection, a linklayer multicast listener command to each constrained wireless networkdevice via the associated wired gateway, the link layer multicastlistener command specifying a listening interval selected by themanagement device, the link layer multicast listener command causingeach constrained wireless network device in response to receipt thereofto change from a low-power optimized mode to a listening mode untilreception of a multicast data packet within the listening interval;generating, by the management device, a set of collision avoidanceparameters for execution by each wired gateway, the collision avoidanceparameters including a minimum waiting interval, a maximum waitinginterval relative to the listening interval, and a redundancy constant;and sending, by the management device, an instruction to the wiredgateways to selectively transmit the multicast data packet based on thecollision avoidance parameters, the instruction causing each wiredgateway to wait a randomly-selected wait interval, relative to theminimum waiting interval and the maximum waiting interval, and after thewait interval selectively transmit the multicast data packet only if areceived number of the multicast data packet by the corresponding wiredgateway is less than the redundancy constant.
 2. The method of claim 1,further comprising: identifying a maximum idle interval corresponding toinitiation of a second listening interval for a second multicast packetfollowing initiation of the listening interval of the multicast datapacket; outputting, to one of each wired gateway or each constrainedwireless network device via the corresponding associated wired gateway,the maximum idle interval by the initiation of the first listeninginterval, the maximum idle interval causing each constrained wirelessnetwork device to enter the low-power optimized mode, in response toreceipt of the multicast data packet, until the initiation of the secondlistening interval.
 3. The method of claim 2, wherein: the maximum idleinterval is sent by the management device to each wired gateway; themaximum idle interval causes each wired gateway to calculate anext-listening interval, relative to the maximum idle interval minus acorresponding transmission time instance of the multicast data packet bythe corresponding wired gateway, and transmit the next-listeninginterval with the multicast data packet; the next-listening intervalcausing the wireless network device to resume the listening mode,following entering the low-power optimized mode, for the initiation ofthe second listening interval.
 4. The method of claim 2, furthercomprising the management device recalculating the maximum idle intervalfor initiation of a third listening interval for a third multicastpacket following the initiation of the second listening interval of thesecond multicast data packet.
 5. The method of claim 2, wherein theoutputting includes inserting the maximum idle interval into the linklayer multicast listener command.
 6. The method of claim 2, furthercomprising fragmenting a received data structure into the at least themulticast data packet and the second multicast packet, for distributionof the data structure to the constrained wireless network devices. 7.The method of claim 1, wherein the management device generates a secondset of collision avoidance parameters for at least one of the wiredgateways determined by the management device to have priority overothers of the wired gateways.
 8. One or more non-transitory tangiblemedia encoded with logic for execution by a machine and when executed bythe machine operable for: generating and sending, by the machineimplemented as a management device for a low power wide area networkcomprising wired gateways and constrained wireless network devices eachassociated with one or more of the wired gateways via a link layerconnection, a link layer multicast listener command to each constrainedwireless network device via the associated wired gateway, the link layermulticast listener command specifying a listening interval selected bythe management device, the link layer multicast listener command causingeach constrained wireless network device in response to receipt thereofto change from a low-power optimized mode to a listening mode untilreception of a multicast data packet within the listening interval;generating, by the management device, a set of collision avoidanceparameters for execution by each wired gateway, the collision avoidanceparameters including a minimum waiting interval, a maximum waitinginterval relative to the listening interval, and a redundancy constant;and sending, by the management device, an instruction to the wiredgateways to selectively transmit the multicast data packet based on thecollision avoidance parameters, the instruction causing each wiredgateway to wait a randomly-selected wait interval, relative to theminimum waiting interval and the maximum waiting interval, and after thewait interval selectively transmit the multicast data packet only if areceived number of the multicast data packet by the corresponding wiredgateway is less than the redundancy constant.
 9. The one or morenon-transitory tangible media of claim 8, further operable for:identifying a maximum idle interval corresponding to initiation of asecond listening interval for a second multicast packet followinginitiation of the listening interval of the multicast data packet;outputting, to one of each wired gateway or each constrained wirelessnetwork device via the corresponding associated wired gateway, themaximum idle interval by the initiation of the first listening interval,the maximum idle interval causing each constrained wireless networkdevice to enter the low-power optimized mode, in response to receipt ofthe multicast data packet, until the initiation of the second listeninginterval.
 10. The one or more non-transitory tangible media of claim 9,wherein: the maximum idle interval is sent by the management device toeach wired gateway; the maximum idle interval causes each wired gatewayto calculate a next-listening interval, relative to the maximum idleinterval minus a corresponding transmission time instance of themulticast data packet by the corresponding wired gateway, and transmitthe next-listening interval with the multicast data packet; thenext-listening interval causing the wireless network device to resumethe listening mode, following entering the low-power optimized mode, forthe initiation of the second listening interval.
 11. The one or morenon-transitory tangible media of claim 9, further operable for themanagement device recalculating the maximum idle interval for initiationof a third listening interval for a third multicast packet following theinitiation of the second listening interval of the second multicast datapacket.
 12. The one or more non-transitory tangible media of claim 9,wherein the outputting includes inserting the maximum idle interval intothe link layer multicast listener command.
 13. The one or morenon-transitory tangible media of claim 9, further operable forfragmenting a received data structure into the at least the multicastdata packet and the second multicast packet, for distribution of thedata structure to the constrained wireless network devices.
 14. The oneor more non-transitory tangible media of claim 8, wherein the managementdevice generates a second set of collision avoidance parameters for atleast one of the wired gateways determined by the management device tohave priority over others of the wired gateways.
 15. A methodcomprising: receiving, by a wired gateway providing a wireless linklayer connection for one or more constrained wireless network devices ina low power wide area network, a link layer multicast listener commandfor each of the one or more constrained wireless network devices, eachlink layer multicast listener command received via a wired connectionwith a management device and specifying a listening interval;transmitting, by the wired gateway, each link layer multicast listenercommand to the corresponding constrained wireless network device, thelink layer multicast listener command causing the correspondingconstrained wireless network device in response to receipt thereof tochange from a low-power optimized mode to a listening mode untilreception of a multicast data packet within the listening interval;receiving an instruction, from the management device, for selectivetransmission of the multicast data packet based on collision avoidanceparameters specified in the instruction, the collision avoidanceparameters including a minimum waiting interval, a maximum waitinginterval relative to the listening interval, and a redundancy constant;and selectively transmitting, by the wired gateway, the multicast datapacket based on randomly selecting a wait interval relative to theminimum waiting interval and the maximum waiting interval, waiting thewait interval following initiation of the listening interval, and afterthe wait interval selectively transmitting the multicast data packetonly if the wired gateway has wirelessly received less than theredundancy constant of the multicast data packets from one or more otherwired gateways.
 16. The method of claim 15, further comprising:receiving, from the management device via the wired connection, amaximum idle interval corresponding to initiation of a second listeninginterval for a second multicast packet following initiation of thelistening interval of the multicast data packet; identifying, by thewired gateway, a first transmission time instance for the multicast datapacket by the wired gateway; calculating a next-listening interval,relative to the maximum idle interval minus the transmission timeinstance; and transmitting the next-listening interval with thetransmission of the multicast data packet, the next-listening intervalcausing each constrained wireless network device to enter the low-poweroptimized mode in response to receipt of the multicast data packet, andresume the listening mode upon initiation of the second listeninginterval.
 17. The method of claim 15, wherein the multicast data packetis one of a plurality of multicast data fragments of a data structure,each multicast data fragment having a corresponding listen interval forreception by the constrained wireless network devices, the methodfurther comprising: receiving, by the wired gateway from one of theconstrained wireless network devices, a bitmap identifying receivedmulticast data fragments of the data structure; identifying, by thewired gateway based on the bitmap, missing multicast data fragments thatwere not received by the one wireless network device; and unicasttransmitting, by the wired gateway, the missing multicast data fragmentsto the one constrained wireless network device, enabling the oneconstrained wireless network device to recover the data structure fromthe multicast data fragments.
 18. One or more non-transitory tangiblemedia encoded with logic for execution by a machine and when executed bythe machine operable for: receiving, by the machine implemented as awired gateway providing a wireless link layer connection for one or moreconstrained wireless network devices in a low power wide area network, alink layer multicast listener command for each of the one or moreconstrained wireless network devices, each link layer multicast listenercommand received via a wired connection with a management device andspecifying a listening interval; transmitting, by the wired gateway,each link layer multicast listener command to the correspondingconstrained wireless network device, the link layer multicast listenercommand causing the corresponding constrained wireless network device inresponse to receipt thereof to change from a low-power optimized mode toa listening mode until reception of a multicast data packet within thelistening interval; receiving an instruction, from the managementdevice, for selective transmission of the multicast data packet based oncollision avoidance parameters specified in the instruction, thecollision avoidance parameters including a minimum waiting interval, amaximum waiting interval relative to the listening interval, and aredundancy constant; and selectively transmitting, by the wired gateway,the multicast data packet based on randomly selecting a wait intervalrelative to the minimum waiting interval and the maximum waitinginterval, waiting the wait interval following initiation of thelistening interval, and after the wait interval selectively transmittingthe multicast data packet only if the wired gateway has wirelesslyreceived less than the redundancy constant of the multicast data packetsfrom one or more other wired gateways.
 19. The one or morenon-transitory tangible media of claim 18, further operable for:receiving, from the management device via the wired connection, amaximum idle interval corresponding to initiation of a second listeninginterval for a second multicast packet following initiation of thelistening interval of the multicast data packet; identifying, by thewired gateway, a first transmission time instance for the multicast datapacket by the wired gateway; calculating a next-listening interval,relative to the maximum idle interval minus the transmission timeinstance; and transmitting the next-listening interval with thetransmission of the multicast data packet, the next-listening intervalcausing each constrained wireless network device to enter the low-poweroptimized mode in response to receipt of the multicast data packet, andresume the listening mode upon initiation of the second listeninginterval.
 20. The one or more non-transitory tangible media of claim 18,wherein the multicast data packet is one of a plurality of multicastdata fragments of a data structure, each multicast data fragment havinga corresponding listen interval for reception by the constrainedwireless network devices, further operable for: receiving, by the wiredgateway from one of the constrained wireless network devices, a bitmapidentifying received multicast data fragments of the data structure;identifying, by the wired gateway based on the bitmap, missing multicastdata fragments that were not received by the one wireless networkdevice; and unicast transmitting, by the wired gateway, the missingmulticast data fragments to the one constrained wireless network device,enabling the one constrained wireless network device to recover the datastructure from the multicast data fragments.